HL-60 cells, a human acute progranulocytic leukemia, and normal (CFUc) are growth inhibited by thymidine. Thymidine affects more than deoxyribonucleotide synthesis. Deoxyguanosine and cytosine arabinoside act synergistically to inhibit HL-60 and K562 cloning efficiency. HL-60 and K562 surface antigens are studied by specific iodine and tritium labeling. Cell surface specific, plant isolectins from phaseolus vulgaris have been confirmed to have a homo and hetero tetrameric conformation.